Automated multiple-instance spanning tree reconfiguration

ABSTRACT

One embodiment relates to a method of automated multiple-instance spanning tree reconfiguration. Query packets are sent to switches within an multiple-instance spanning tree (MST) region, and response packets are received from the switches with traffic utilization data for ports of the switches. An MST reconfiguration is determined. The MST reconfiguration is propagated to the switches within the MST region. Other embodiments and features are also disclosed.

BACKGROUND

1. Field of the Invention

The present disclosure relates generally to computer networking. Moreparticularly, the present disclosure relates to spanning tree protocols.

2. Description of the Background Art

Spanning tree protocol (STP) and its variants, including rapid spanningtree protocol (RSTP) and multiple-instance spanning tree protocol(MSTP), are link management protocols that prevent undesirable loops ina network while allowing for path redundancy. Undesirable loops occurwhen there are multiple active paths between stations. If a loop exists,a switch or bridge may see stations appearing on more than one link ofthe switch. This can confuse the forwarding algorithm, allowingduplicate frames to be forwarded. Further, multicast traffic enteringthe loop multiplies, but never leaves the loop, eventually bringing thenetwork down.

STP computes a tree that spans all switches in an extended network andforces select redundant data paths into a standby or blocked state. Ifone segment of the network becomes unreachable, STP can re-establishconnectivity to that segment by activating a standby path. In order toaccomplish this, one switch (bridge) is designated as the root of thespanning tree. STP is a distributed protocol and relies on the exchangeof messages between neighbors to compute and implement the spanningtree. When there are changes in the network due to failure or equipmentupgrades, the protocol needs to recompute the tree. During such times,the forwarding of traffic may be disrupted for a period of time,sometimes referred to as the convergence time of the protocol, which canrange from milliseconds to seconds.

The traditional spanning tree protocol (IEEE 802.1d) is limited to onlyone path through the spanning tree environment. Multiple-instancespanning tree protocol (MSTP) (IEEE 802.1.s) addresses this limitation.MSTP allows multiple spanning tree instances, each instance providing adifferent path through the multiple-instance spanning tree (MST) region.With MSTP, numerous virtual local area networks (VLANs) may be mapped tovarious MSTP instances.

SUMMARY

One embodiment relates to a method of automated multiple-instancespanning tree reconfiguration. Query packets are sent to switches withinan multiple-instance spanning tree (MST) region, and response packetsare received from the switches with traffic utilization data for portsof the switches. An MST reconfiguration is determined. The MSTreconfiguration is propagated to the switches within the MST region.

Another embodiment pertains to a network management apparatus thatincludes a processor, memory for storing processor-executableinstructions and data, an internal communication system, and at leastone port. The memory includes a) processor-executable code configured todetermine an MST reconfiguration; and b) processor-executable codeconfigured to send packets to multiple-instance spanning tree protocol(MSTP) enabled switches within a MST region so as to propagate said MSTreconfiguration.

Another embodiment pertains to a network switching apparatus whichincludes memory for storing processor-executable instructions and data.The memory includes a) processor-executable code configured to obtaintraffic utilization data for all ports of the apparatus when a querypacket for the traffic utilization data is received; b)processor-executable code configured to send a response packet in replyto the query packet, wherein the response packet includes the trafficutilization data; and c) processor-executable code configured to replacea prior multiple-instance configuration with a new multiple-instanceconfiguration.

Other embodiments and features are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram depicting an example network ofMSTP-enabled switches for discussing the operation of the disclosedtechnique in accordance with an embodiment of the invention.

FIGS. 2A, 2B and 2C are schematic diagrams depicting three MSTPinstances of the example network of FIG. 1.

FIG. 3 is a schematic diagram of an example switch which may be a nodeof the example network of FIG. 1.

FIG. 4 is a schematic diagram of an example network management stationwhich may be configured to manage the example network of FIG. 1.

FIG. 5 is a flow chart depicting a method of multiple-instance spanningtree reconfiguration in accordance with an embodiment of the invention.

FIG. 6 is a flow chart depicting a method of multiple-instance spanningtree reconfiguration which depends on traffic priority in accordancewith an embodiment of the invention.

FIG. 7 is a flow chart depicting a method of multiple-instance spanningtree reconfiguration which is event triggered in accordance with anembodiment of the invention.

FIG. 8 is a flow chart depicting a method of multiple-instance spanningtree reconfiguration which is scheduled in accordance with an embodimentof the invention.

FIG. 9 is a flow chart depicting a method performed at an MSTP-enabledswitch in the MST region in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION

As discussed above, multiple-instance spanning tree protocol (MSTP)allows the use of multiple spanning tree instances, each instanceproviding a different path through the multiple-instance spanning tree(MST) region. With MSTP, numerous virtual local area networks (VLANs)may be mapped to various MSTP instances.

A drawback to MSTP is the administrative burden relating to manuallyconfiguring the multiple-instance spanning tree. Determining the way todivide the VLANs into groups for assignment to the MSTP instances, andconfiguring the appropriate ports to be blocked, may be difficult.Moreover, once configured, the configuration usually remains static anddoes not typically change.

The present disclosure provides methods and apparatus for automatedmultiple-instance spanning tree reconfiguration. In other words, thetechniques disclosed herein relates to automated and dynamicre-organization of the mappings of VLANs to MSTP instances based ontraffic conditions within the network.

FIG. 1 is a diagram depicting an example network topology for discussingthe operation of the disclosed technique in accordance with anembodiment of the invention. The example network includes four switches(bridges) 102 with five communication links interconnecting them asshown.

The four switches 102 are labeled A, B, C, and D. The pertinent ports ofthe switches are labeled by numbers for purposes of identification inthe following discussion.

In this particular example, a first link interconnects port 2 of switchA to port 3 of switch B. A second link interconnects port 5 of switch Bto port 10 of switch D. A third link interconnects port 9 of switch D toport 8 of switch C. A fourth link interconnects port 6 of switch C toport 1 of switch A. Finally, a fifth link interconnects port 4 of switchB to port 7 of switch C. A network management server 104 is shown asbeing interconnected with the network by way of port 11 of switch D.

FIGS. 2A, 2B and 2C are schematic diagrams depicting three MSTPinstances of the example network of FIG. 1. The network may supportnumerous virtual local area networks (VLANs). For example, up to 4,096VLANs may be supported. Each of the switches 102 includes a table thatassociates each VLAN to one of the MSTP instances. In this example,several VLANs are mapped onto each of the three MSTP instances.

Detailed configurations of these three MSTP instances are describedbelow for purposes of discussing the present invention. Of course, inactual practice, the number of switches may be more or less than four,the number of MSTP instances may be more or less than three, and thedetailed configurations of the MSTP instances will vary depending on thespecific network and other circumstances.

FIG. 2A depicts a first MSTP instance (MSTP instance 1). Three VLANs(having VLAN identifiers 40, 41 and 42) are mapped to MSTP instance 1.MSTP instance 1 has switch D as the root switch. Ports 1 and 4 areblocked in MSTP instance 1. More specifically, the port roles are asfollows. Ports 8, 5, and 2 are root ports. Ports 9, 10, 3, 6, and 7 aredesignated ports. Finally, ports 1 and 4 are alternate ports (which areblocking ports).

FIG. 2B depicts a second MSTP instance (MSTP instance 2). Three VLANs(having VLAN identifiers 5, 7, and 2048) are mapped to MSTP instance 2.MSTP instance 2 has switch C as the root switch. Ports 3 and 5 areblocked in MSTP instance 2. More specifically, the port roles are asfollows. Ports 1, 4 and 9 are root ports. Ports 6, 7, 8, 2, and 10 aredesignated ports. Finally, ports 3 and 5 are alternate ports (which areblocking ports).

FIG. 2C depicts a third MSTP instance (MSTP instance 3). Three VLANs(having VLAN identifiers 4000, 2100, and 4108) are mapped to MSTPinstance 3. MSTP instance 3 has switch B as the root switch. Ports 6 and8 are blocked in MSTP instance 3. More specifically, the port roles areas follows. Ports 2, 7, and 10 are root ports. Ports 3, 4, 5, 1, and 9are designated ports. Finally, ports 6 and 8 are alternate ports (whichare blocking ports).

FIG. 3 is a schematic diagram of an example switch 102 which may be anode of the example network of FIG. 1. The specific configuration of theswitches, bridges, or similar such network devices within a network willvary depending on the specific implementation of the network.

A central processing unit (CPU) 302 performs overall configuration andcontrol of the switch 300 operation. The CPU 302 operates in cooperationwith switch control 304, an application specific integrated circuit(ASIC) designed to assist CPU 302 in performing packet switching at highspeeds required by modern networks.

The switch control 304 controls the “forwarding” of received packets toappropriate locations within the switch for further processing and/orfor transmission out another switch port. Inbound and outbound highspeed FIFOs (306 and 308, respectively) may be included with the switchcontrol 304 for exchanging data over a switch bus 350 with port modules.

Memory 310 may include inbound/outbound queues 312, variousprocessor-executable code routines 314, and other data 316. Theprocessor-executable code routines 314 may include those for executingthe operations relating to multiple instance spanning tree protocol. Inaccordance with an embodiment of the invention, the routines 314 mayalso be configured to implement operations relating to the automatedmultiple-instance spanning tree reconfiguration, for example, such asthose discussed below in relation to FIG. 9. A communications bus 352may interconnect the CPU 302, switch control 304, and memory 310.

The ports of the switch may be embodied as plug-in modules that connectto the switch bus 350. Each such module may be, for example, amulti-port module 318 having a plurality of ports (for example, 320through 328) in a single module or may be a single port module 336having a single port 337.

As packets are received from a port, the packet data may be applied tothe switch bus 320 in such a manner as to permit monitoring of thepacket data by switch control 304. The switch control 304 may beconfigured to manage access to switch bus 350 by all port modules (i.e.,318 and 336). All port modules may “listen” to packets as they arereceived and applied by a receiving port module to switch bus 350.

FIG. 4 is a schematic diagram of an example network management server104 which may be configured to manage the example network of FIG. 1. Inthe example depicted in FIG. 1, the network management server 104 isinterconnected to Switch D. (Of course, the server could beinterconnected to any other of the switches instead.) The server 104executes network management software so as to manage the network. Inthis example, the network management server 104 includes a processor402, memory 404, communication bus(es) 406, input/output interfaces 408,a display 410, a keyboard 412, and a mouse 414.

The memory 404 is configured to store processor-executable code 405 andother data. The communication bus or buses 406 are configured tocommunicatively couple components within the apparatus, such as theprocessor, memory and input/output interfaces. The input/outputinterfaces 408 includes at least one port communicatively coupled toanother device in the network. The port may comprise, for example, anethernet type port.

The processor-executable code 405 in the memory 404 may be configured toperform various network management functionalities, including theoperations for automated multiple-instance spanning tree reconfigurationas disclosed herein and discussed in detail below in relation to FIGS.5, 6, 7, and 8.

FIG. 5 is a flow chart depicting a method 500 of multiple-instancespanning tree reconfiguration in accordance with an embodiment of theinvention. This method 500 may be performed, for example, using anexternal network management server 104.

In this embodiment, the server 104 may periodically poll all of theswitches within the MSTP environment (MST region) for trafficutilization on all of the switch ports. When a polling time is reached(i.e. when it is time for the periodic polling to be performed) 502, theserver 104 may send 504 query packets to the switches 102 within the MSTregion.

When one of the MSTP-enabled switches 102 receives the query, it obtainstraffic utilization related data to be sent back in a response. Thetraffic utilization related data may include, for example, remotemonitoring (RMON) counters, port queue depths, numbers of packetstransmitted and dropped, and other traffic utilization related data.

The server 104 receives 506 the response packets from the variousswitches 102 in the MST region. Based on the traffic utilization data,processor-executable code in the server 104 may determine 508 whetherthe data indicates that a multiple-instance spanning treereconfiguration would be substantially beneficial.

If a reconfiguration would not be substantially beneficial, then noreconfiguration is performed, and the method 500 may proceed to wait 510until the next polling time is reached 502.

On the other hand, if a reconfiguration would be substantiallybeneficial, then a determination 512 is made of a specificreconfiguration to substantially improve performance. For example, thedetermination 512 may be made so as to maximize the overall performanceof the network in the MST region and also to minimize the possibility oftraffic loss.

The new multiple-instance spanning tree configuration may then be sent514 from the server 104 to the switches 102. In one implementation,simple network management protocol (SNMP) may be used to send 514 thenew configuration from the server 104 to the switches 102. Thereafter,the method 500 may proceed to wait 510 until the next polling time isreached 502.

For example, consider the multiple-instance spanning tree configurationdepicted in FIGS. 2A, 2B and 2C. Consider further that the link betweenswitches C and D is over utilized on VLANs 40 and 41 (which are mappedto MSTP instance 1). Meanwhile, the link between switches B and C isonly lightly utilized by the VLANs mapped to MSTP instances 2 and 3, andthe link between switches C and D is also only lightly utilized by theVLANs mapped to MSTP instance 3. In that case, a multiple-instancespanning tree reconfiguration may be substantially beneficial. Forexample, the reconfiguration which is determined 512 may re-map VLAN 40(or alternatively VLAN 41) from MSTP instance 1 to MSTP instance 3.After such a reconfiguration, the traffic on VLAN 40 between switches Cand D will no longer travel across the direct link between switches Cand D. This will relieve the over utilization of that link. Instead, thetraffic on VLAN 40 between switches C and D will travel on the pathgoing from switch C to switch B to switch D. Alternatively or inaddition to such remappings of VLANs to MSTP instances, other types ofMST reconfigurations may be determined 512. For example, MSTP parameters(such as, for instance, port path costs and port priorities) may bemodified. Modifying these MSTP parameters may result in a change of theblocking scheme.

FIG. 6 is a flow chart depicting a method 600 of multiple-instancespanning tree reconfiguration which depends on traffic priority inaccordance with an embodiment of the invention. This method 600 may beperformed, for example, using an external network management server 104.The method 600 of FIG. 6 differs from the method 500 of FIG. 5 in thatthe method 600 of FIG. 6 considers VLAN traffic prioritization indetermining 608 a need for reconfiguration and in determining 612 thespecific reconfiguration to be made.

In this embodiment, the server 104 may periodically poll all of theswitches within the MSTP environment (MST region) for trafficutilization on all of the switch ports. When a polling time is reached(i.e. when it is time for the periodic polling to be performed) 602, theserver 104 may send 604 query packets to the switches 102 within the MSTregion.

When one of the MSTP-enabled switches 102 receives the query, it obtainstraffic utilization related data to be sent back in a response. Thetraffic utilization related data may include, for example, remotemonitoring (RMON) counters, port queue depths, numbers of packetstransmitted and dropped, and other traffic utilization related data.

The server 104 receives 606 the response packets from the variousswitches 102 in the MST region. Based on the traffic utilization data,processor-executable code in the server 104 may determine 608 whetherthe data indicates that a multiple-instance spanning treereconfiguration is needed. This determination 608 takes into account thetraffic priorities assigned to the various VLANs. For example, if ahigher priority VLAN has substantially poorer performance statistics anda larger number of packets lost compared with lower priority VLANs, thena reconfiguration may be needed.

If a reconfiguration is not needed then no reconfiguration is performed,and the method 600 may proceed to wait 610 until the next polling timeis reached 602.

On the other hand, if a reconfiguration would be substantiallybeneficial, then a determination 612 is made of a specificreconfiguration. If a higher priority VLAN has unacceptably poorperformance, then the specific reconfiguration may improve performanceon that VLAN. In the example network discussed above in relation toFIGS. 2A, 2B and 2C, VLAN 4000 may be set to a higher priority fortraffic than the other VLANs. In that case, the performance of VLAN 4000would be given a higher priority when re-mapping VLANs to MSTPinstances. Alternatively or in addition to such remappings of VLANs toMSTP instances, other types of MST reconfigurations may be determined612. For example, MSTP parameters (such as, for instance, port pathcosts and port priorities) may be modified. Modifying these MSTPparameters may result in a change of the blocking scheme.

The new multiple-instance spanning tree configuration may then be sent614 from the server 104 to the switches 102. In one implementation,simple network management protocol (SNMP) may be used to send 614 thenew configuration from the server 104 to the switches 102. Thereafter,the method 600 may proceed to wait 610 until the next polling time isreached 602.

FIG. 7 is a flow chart depicting a method 700 of multiple-instancespanning tree reconfiguration which is event triggered in accordancewith an embodiment of the invention. In accordance with this method 700,the MST reconfiguration procedure may be triggered 702 by an event inthe network.

For example, consider a link or switch failure in the MST region. When alink or switch fails, MSTP will reconfigure the spanning trees andchange the layouts of the MSTP instances. This reconfiguration of thespanning tree instances to accommodate the changed network topology maytrigger 702 a reconfiguration procedure to better optimize the mappingof VLANs to MSTP instances in accordance with an embodiment of theinvention. Such a reconfiguration procedure may be desirable because thetraffic utilization pattern in the MST region changes with the newtopology.

Once the reconfiguration procedure is triggered 702, the server 104 maysend 704 query packets to the switches 102 within the MST region. Whenone of the MSTP-enabled switches 102 receives the query, it obtainstraffic utilization related data to be sent back in a response. Thetraffic utilization related data may include, for example, remotemonitoring (RMON) counters, port queue depths, numbers of packetstransmitted and dropped, and other traffic utilization related data.

The server 104 receives 706 the response packets from the variousswitches 102 in the MST region. Based on the traffic utilization data,processor-executable code in the server 104 may determine 708 a specificreconfiguration to improve or optimize performance. For example, thedetermination 708 may be made so as to maximize the overall performanceof the network in the MST region and also to minimize the possibility oftraffic loss. The determination 708 may also take into accountprioritization of traffic on the VLANs.

The new multiple-instance spanning tree configuration may then be sent710 from the server 104 to the switches 102. In one implementation,simple network management protocol (SNMP) may be used to send 710 thenew configuration from the server 104 to the switches 102.

FIG. 8 is a flow chart depicting a method 800 of multiple-instancespanning tree reconfiguration which is scheduled in accordance with anembodiment of the invention.

Consider a network where network traffic or bandwidth requirements arehigher at different times of the day. For example, consider that abackup process occurs on VLAN 7 (on MSTP instance 2 per FIG. 2B) frommidnight to 2 am at night.

When a first scheduled time (in this case, midnight) is reached 802 afirst scheduled reconfiguration may be propagated 804, for example, toreconfigure the mapping of VLANs to MSTP instances to an alternatemapping so as to provide VLAN 7 with large bandwidth. Besides or inaddition to such re-mappings, other types other types of MSTreconfigurations may be propagated 804. For example, MSTP parameters(such as, for instance, port path costs and port priorities) may bechanged.

When a second scheduled time (in this case, 2 am) is reached 806 asecond scheduled reconfiguration may be propagated 808 to return to theoriginal MST configuration.

FIG. 9 is a flow chart depicting a method 900 performed at anMSTP-enabled switch 102 in the MST region in accordance with anembodiment of the invention. Processor-executable code and/or circuitrywithin the switch 102 may be configured to perform the steps shown inFIG. 9.

The switch 102 may receive 902 a query packet sent by a server 104. Inthis case, the query packet may request that the switch 102 returntraffic utilization data for its ports. The switch 102 then proceeds toobtain 904 the traffic utilization data. The traffic utilization datamay include, for example, remote monitoring (RMON) counters, port queuedepths, numbers of packets transmitted and dropped, and other trafficutilization related data. The switch 102 may then send 906 the trafficutilization data back to the server 104 via response packets.

Subsequently, if the server 104 decides to propagate a multiple-instancespanning tree reconfiguration, then a new multiple-instance spanningtree configuration may be received 908 by the switch 102. For example,the new multiple-instance spanning tree configuration may include datathat re-maps VLANs to MSTP instances, or it may include new MSTparameters (such as new port path costs and/or port priorities). Theswitch 102 replaces or updates 910 the prior MST configuration with thenew MST configuration.

In the above description, numerous specific details are given to providea thorough understanding of embodiments of the invention. However, theabove description of illustrated embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. One skilled in the relevant art will recognize that theinvention can be practiced without one or more of the specific details,or with other methods, components, etc. In other instances, well-knownstructures or operations are not shown or described in detail to avoidobscuring aspects of the invention. While specific embodiments of, andexamples for, the invention are described herein for illustrativepurposes, various equivalent modifications are possible within the scopeof the invention, as those skilled in the relevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific embodimentsdisclosed in the specification and the claims. Rather, the scope of theinvention is to be determined by the following claims, which are to beconstrued in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. A method of automated multiple-instance spanningtree reconfiguration, the method comprising: detecting a firsttriggering event comprising an initial reconfiguration of amultiple-instance spanning tree (MST) instances due to failure of a linkor switch within an MST region; in response to detecting the firsttriggering event, sending query packets to switches within the MSTregion, said query packets requesting statistics for measured datatraffic for ports of the switches; receiving response packets from theswitches, said response packets containing said statistics for measureddata traffic for the ports of the switches; determining an MSTreconfiguration based on the statistics for measured data traffic forthe ports of the switches; and propagating the MST reconfiguration tothe switches within the MST region.
 2. The method of claim 1, whereinthe MST reconfiguration comprises a re-mapping of virtual local areanetworks (VLANs) to multiple-instance spanning tree protocol (MSTP)instances to move at least one VLAN from one MST instance to another MSTinstance.
 3. The method of claim 1, wherein the MST reconfigurationcomprises a modification of MST parameters.
 4. The method of claim 1,wherein the query packets are sent periodically to poll the switches asto the statistics for the measured data for the ports of the switches.5. The method of claim 1, wherein the reconfiguration is determined toimprove network performance within the MST region.
 6. The method ofclaim 5, wherein the reconfiguration is further determined to decrease arate of dropped packets by the switches.
 7. The method of claim 1,wherein the reconfiguration is determined in dependence of VLAN trafficpriorities to increase performance on a higher priority VLAN.
 8. Themethod of 1, further comprising: reconfiguring the MST instances toaccommodate at a first scheduled network traffic change having a starttime and an end time; and after the end time, returning the MSTinstances to a prior configuration.
 9. A network management apparatusfor a network, the apparatus comprising: a processor; memory for storingprocessor-executable instructions and data; a communication system forcommunicatively coupling components within the network managementapparatus; and at least one port communicatively coupled to anotherdevice in the network, wherein the memory includes a)processor-executable code to determine an multiple instance spanningtree (MST) reconfiguration based on statistics for measured data trafficfor the at least one port, said statistics being received from said atleast one port, wherein the reconfiguration comprises a scheduledreconfiguration to accommodate a predetermined change in networktraffic; and b) processor-executable code to send packets tomultiple-instance spanning tree protocol (MSTP) enabled switches withina MST region to propagate said MST reconfiguration.
 10. The apparatus ofclaim 9, wherein the MST reconfiguration comprises a re-mapping ofvirtual local area networks (VLANs) to multiple-instance spanning treeprotocol (MSTP) instances to move at least one VLAN from one MSTinstance to another MST instance.
 11. The apparatus of claim 9, whereinthe MST reconfiguration comprises a modification of MST parameterscomprising port path costs and port priorities.
 12. The apparatus ofclaim 9, further comprising: processor-executable code to send querypackets to switches within an multiple-instance spanning tree (MST)region, where the query packets request statistics for measured datatraffic for ports of the switches; and processor-executable code toreceive and process response packets from the switches with thestatistics for measured data traffic for the ports of the switches. 13.The apparatus of claim 12, wherein the query packets are sentperiodically to poll the switches as to the statistics for measured datatraffic for the ports of the switches.
 14. The apparatus of claim 12,wherein the query packets are sent after a triggering event.
 15. Theapparatus of claim 14, wherein the triggering event comprises areconfiguration of the MST instances due to a failed link or switchwithin the MST region.
 16. The apparatus of claim 9, wherein thescheduled reconfiguration comprises a start time and an end time. 17.The apparatus of claim 9, wherein the reconfiguration is determined toimprove network performance within the MST region.
 18. The apparatus ofclaim 9, wherein the reconfiguration is determined in dependence of VLANtraffic priorities, and wherein the reconfiguration is determined toincrease performance on a higher priority VLAN.
 19. A network switchingapparatus, the apparatus comprising: a processor; memory for storingprocessor-executable instructions and data; a communication system forcommunicatively coupling components within the apparatus; and at leastone port communicatively coupled to another device in the network,wherein the memory includes a) processor-executable code to obtainstatistics for measured data traffic for all ports of the apparatus whena query packet requesting the statistics for measured data traffic isreceived; b) processor-executable code to send a response packet inreply to the query packet, wherein the response packet includes thestatistics for measured traffic utilization; c) processor-executablecode to replace a first multiple-instance configuration with a secondmultiple-instance configuration based on the statistics for measureddata traffic; d) processor-executable code to reconfigure the secondmultiple instance configuration to accommodate at a scheduled networktraffic change having a start time and an end time; and e)processor-executable code to return to the second multiple instanceconfiguration after the end time.